Rules: Add rules for yum commands, #470

[m-ildefons]

Add four rules for yum commands warning on bad practices:

• yum update
• yum install without non-interactive flag -y
• yum install -y <pkg> without version pinning
• yum install ... without also cleaning up with yum clean all

These four rules are accompanied by test for each rule.
Also included is a new helper function Shell.anyCommands.

What I did

Add four rules for linting yum commands in RUN layers. These four rules check for common mistakes and bad-practices with yum in Dockerfiles.
This PR is related to #470, but does not suffice to close it since zypper and dnf checks are still missing.

How I did it

I expanded the Rules.hs file. I also added a new helper function in the Shell.hs file: Shell.anyCommands that works like Shell.allCommands, except it matches on any instead of all commands in a shell line.

How to verify it

Run the test suite, or run hadolint on this Dockerfile:

FROM centos:8
RUN yum update
RUN yum install httpd
RUN yum install -y tomcat
RUN yum install -y mariadb-10.4
RUN yum install -y php-7.2 && yum clean all

The FROM and the last RUN yum install.. line will not produce warnings and the other lines will each trigger a different combination of warnings for yum.

[lorenzo]

looking great! I wonder why the travis build did not start

[lorenzo]

some tests are failing too, but they seem easy to fix

[m-ildefons]

Thanks. I fixed the overzealous clean all rule. Now it should no longer falsely flag RUN layers that don't even contain yum commands.

[lorenzo]

@m-ildefons Would you mind adding the corresponding wiki pages for the new DL codes? I think they can just be compies of the similar codes for apt

[lorenzo]

Thanks so much for your contribution!

[lorenzo]

ah, I merged too quickly and I just found this is a typo Sepcify @m-ildefons